docs: def friction_plate_Muley_Manglik(Re, chevron_angle, plate_enlargement_factor):
      r'''Calculates Darcy friction factor for single-phase flow in a 
      Chevron-style plate heat exchanger according to [1]_, also shown and
      recommended in [2]_.
      
      .. math::
          f_f = [2.917 - 0.1277\beta + 2.016\times10^{-3} \beta^2]
          \times[20.78 - 19.02\phi + 18.93\phi^2 - 5.341\phi^3]
          \times Re^{-[0.2 + 0.0577\sin[(\pi \beta/45)+2.1]]}
          
      Parameters
      ----------
      Re : float
          Reynolds number with respect to the hydraulic diameter of the channels,
          [-]
      chevron_angle : float
          Angle of the plate corrugations with respect to the vertical axis
          (the direction of flow if the plates were straight), between 0 and
          90. Many plate exchangers use two alternating patterns; use their
          average angle for that situation [degrees]
      plate_enlargement_factor : float
          The extra surface area multiplier as compared to a flat plate
          caused the corrugations, [-]
  
      Returns
      -------
      fd : float
          Darcy friction factor [-]
  
      Notes
      -----
      Based on experimental data of plate enacement factors up to 1.5, and valid 
      for Re > 1000 and chevron angles from 30 to 60 degrees with sinusoidal 
      shape. See `PlateExchanger` for further clarification on the definitions.
      
      The length the friction factor gets multiplied by is not the flow path
      length, but rather the straight path length from port to port as if there
      were no chevrons.
      
      This is a continuous model with no discontinuities.
      
      Examples
      --------
      >>> friction_plate_Muley_Manglik(Re=2000, chevron_angle=45, plate_enlargement_factor=1.2)
      1.0880870804075413
  
      References
      ----------
      .. [1] Muley, A., and R. M. Manglik. "Experimental Study of Turbulent Flow
         Heat Transfer and Pressure Drop in a Plate Heat Exchanger With Chevron 
         Plates." Journal of Heat Transfer 121, no. 1 (February 1, 1999): 110-17.
         doi:10.1115/1.2825923.
      .. [2] Ayub, Zahid H. "Plate Heat Exchanger Literature Survey and New Heat
         Transfer and Pressure Drop Correlations for Refrigerant Evaporators." 
         Heat Transfer Engineering 24, no. 5 (September 1, 2003): 3-16. 
         doi:10.1080/01457630304056.
      '''
      beta, phi = chevron_angle, plate_enlargement_factor
      # Beta is indeed chevron angle; with respect to angle of mvoement
      # Still might be worth another check
      t1 = (2.917 - 0.1277*beta + 2.016E-3*beta**2)
      t2 = (5.474 - 19.02*phi + 18.93*phi**2 - 5.341*phi**3)
      t3 = -(0.2 + 0.0577*sin(pi*beta/45. + 2.1))
      # Equation returns fanning friction factor
      return 4*t1*t2*Re**t3